A DC to DC converter may be used to convert an input DC voltage to an output DC voltage. A boost converter is a type of DC to DC converter that converts an input DC voltage into a higher output DC voltage. Such boost converters may be utilized in a variety of electronic devices including portable electronic devices deriving power from a battery source. Usually, the output voltage is regulated to a required value, while the input voltage varies due to battery discharging or to variable load current. The output voltage of the boost converter may be controlled by a controller which controls a state of one or more switches.
One type of control signal provided to the switches may be a pulse width modulated (PWM) signal where the duty cycle of the PWM signal varies to control the state of the switches. In a boost converter utilizing a PWM control signal the current ripple in an associated inductor of the boost converter depends on the duty cycle (D) of the PWM control signal. The inductor current ripple is maximum for D=0.5, and decreases when the duty cycle is either D>0.5 or D<0.5. While designing such a boost converter, the worst case inductor current limit should be taken into consideration. This requires an inductor to support the peak current without saturating the core. For a boost converter controlled by a PWM control signal, the inductor has to be sized for the peak current that occurs at D=0.5, when the input voltage is VIN=VOUT/2. For any other input voltage the peak current will be smaller, thus the inductor will be under utilized. The same under utilization affects all of the boost converter components, including the power switches, and the output and input filtering capacitors meant to smooth the output voltage and filter the input voltage. All these affect negatively the cost, size, and efficiency of the boost converter. Other types of control signals, e.g., pulse frequency modulation (PFM) which varies its frequency, have similar drawbacks as the boost converter controlled by a PWM control signal.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly.